Put the flour, butter, and sugar in a bowl and loosely knead them together with your hands until the mixture becomes crumbly. You can also pulse it briefly in a food processor.

Then add a pinch of salt and gradually add the cold water until you can form the mixture into a ball.

Place the ball of dough in the refrigerator for about half an hour. While the dough is chilling, continue with the filling.

Preheat the oven to 220 degrees Celsius / 428 Fahrenheit with top and bottom heat. Make sure the baking tray is already in the oven so it will also be thoroughly heated.

Peel the peaches and cut them into slices. Remove the pits. Place the peach slices in a bowl and add the sugar, custard powder, and cardamom.

Take the dough out of the refrigerator and divide it into 3 equal balls, or leave it as 1 large ball.

Roll out each ball into a round sheet of dough with a little flour so it doesn't stick to the rolling pin (it can look a bit rustic). If desired, use baking paper underneath so the galette is already on the baking paper and won't stick to the countertop.

Spread one-third of the peach mixture over the center of each galette.

Fold the edges over the filling. If needed, use the baking paper to help fold the dough over the filling while holding the paper. This allows the dough to fall over the filling (with a little help) without sticking to the paper. The dough can tear easily, and this method helps prevent that.

Brush the edge with a beaten egg and sprinkle with the sliced almonds to taste.

Place the galettes in the oven and bake them (one at a time if necessary, depending on the size of your oven) for about 15 minutes until golden brown and cooked through.